It is often desirable to maintain vascular access with a device that simultaneously accommodates multiple use such as the insertion of various devices and the injection or withdrawal of fluids. In emergency and critical care situations, urgently needed medication can be injected through the lumen of an introducer sheath, which already provides for passage of wire guides, catheters, and other devices. Injecting an emergency dose of medication through the introducer sheath at an established vascular access site eliminates the potentially life-threatening time delay of obtaining an additional site. Furthermore, a patient may not have another usable site for vascular access. Therefore, it is desirable that a vascular access introducer sheath be capable of supporting multiple applications and, in particular, simultaneously accommodating the insertion of devices and the injection of fluids, particularly at a controlled infusion rate.
Several possible solutions have been suggested for simultaneously supporting multiple applications. One solution is the use of a single-lumen introducer sheath. A problem with this introducer sheath is that the wire guide or catheter positioned through the lumen occludes the lumen and obstructs the passage of fluid through the lumen. As a result, a small amount of injected medication requires a relatively large "push" of another fluid such as saline to facilitate forcing the medication to the distal end of the sheath. A single-lumen introducer sheath can also include a side port positioned about the proximal end thereof. A proximally positioned side port provides a second avenue of entry to the introducer sheath lumen, but the above-mentioned problem with having only a single lumen remains. Another problem with the side port is that there is dead space in the side port fitting at the proximal end of the sheath lumen where medication and fluids pool. A relatively large "push" of saline dilutes the small dose of medication already backed up and remaining in the dead space. As a result, the "push" serves to force very little medication to the distal end of the sheath and into the bloodstream of a patient. There is also another major problem with single-lumen introducer sheaths, particularly when attempting to infuse medication at a controlled rate. The insertion and withdrawal of devices through a single-lumen introducer sheath interrupts the infusion of medication at a controlled rate, which can be life threatening. Therefore, a single-lumen introducer sheath provides an inefficient means, at best, for the simultaneous passage of various devices and infusion of medication, particularly at a controlled rate.
Another possible solution is the use of a multi-lumen catheter. A problem with using a multi-lumen catheter is that the catheter is typically inserted into the vascular system through an introducer sheath. As a result, there is a time delay for initiating vascular access during the start-up of a procedure, which is particularly critical in an emergency or intensive care situation. Another problem with using a multi-lumen catheter is that the outside diameter of the catheter is significantly larger than that of a single-lumen catheter. As a result, a larger introducer sheath is used, and a larger opening is made in the patient's blood vessel. This large blood vessel opening causes a greater loss of blood and increased risk of complications that may be life threatening in surgical or emergency situations. Alternatively, if the outside diameter of a multi-lumen catheter is desirably small, the lumens of an elastic, soft plastic material catheter are also small, which severely limits the range of devices that can be passed through the catheter.